1. Field of the Invention
The invention relates to improvements in the construction of regenerator furnaces.
2. The Prior Art
Regenerator furnaces are of two types: transverse-burner furnaces and loop furnaces.
Transverse-burner and regenerator furnaces are well known. In this type of furnace, the burners of relatively large size and in small numbers are arranged opposite one another on the sides of the furance and operate alternately, the burners on one of the sides being ignited, whilst those located on the other side are extinguished. The hot smoke escapes via the pipes of the extinguished burners and heats the regenerator stacks. After the burners have been reversed, these hot stacks are used to heat the combustion air conveyed to the burners in operation, whilst the smoke is used to heat the regenerator stack associated with the extinguished burners, and so on and so forth.
Transverse-burner and regenerator furnaces are used especially in glass-making, particularly in large production units for bottles or sheet glass.
In transverse-burner and regenerator furnaces, the combustion air arrives in the furnace via masonry burner pipes which are connected to the upper parts of the regenerators. A certain number of injectors located under the burner platform, in its vault or on the sides, allow the intake of fuel (gas or heavy fuel oil). The flames are of the asymmetric "diffusion flame" type, the air and the fuel arriving separately at a certain angle relative to one another.
This conventional technology has a certain number of disadvantages which can be summarized as follows:
The masonry burner pipes are separated from one another by dead spaces which can reach two meters and sometimes more. Since the flames develop approximately over the width of these pipes, the result is that only some of the surface of the glass bath is covered by the flames, usually 30 to 45%.
Now the heat exchange and therefore the combustion efficiency, and consequently the consumption of the furnace, depend on this percentage covered by the flames.
The flames radiate over the part of the regenerators which is located above the stacks.
This is because of a relatively large solid angle of the burner pipes (these widen from the furnace towards the regenerator). The heat lost in this way represents approximately 3% of the perceptible heat of the smoke, but in contrast to the latter it is, so to speak, unrecoverable.
The construction of the burner pipes is complicated: a keyed vault, heavy reinforcements, etc.
This makes it necessary to use, for assembly, a large and specially trained labour force as well as suitable equipment (arches). Moreover, these pipes are very difficult to insulate, and the "edge effect" plays an appreciable part in the heat losses.
The width of the penetrations of these pipes in the regenerators is small in comparison with the total length of the walls which receive these penetrations. This results in many dead spaces and poor distribution of the smoke in the stacks, and consequently lowers the efficiency of the regenerators.
Finally, because of the reduced number of burners of relatively high power, the pipes are geometrically unsuitable for the furnace chamber, thus causing poor distribution of the fluids (air, fuel) which, in turn, entails a lowering of efficiency which is all the greater because the chamber is large.
Transverse-burner and regenerator furnaces have relatively high fuel consumptions, typically of the order of 1,300 kcal per kg of gas.
Because of the increasing cost of petroleum products, there is a constant need for an improvement in the thermal efficiency of furnaces so as to reduce their fuel consumption.
As regards loop furnaces, these comprise two burners, each equipped with one or more fuel injectors, the two burners being placed next to one another on one and the same side as the furnace. Each burner operates in turn, and the flame coming from a first burner develops along a horseshoe-shaped path, returning towards the second burner, thus forming a loop. The smoke escapes via the pipe of the latter and passes through a regeneration chamber, losing in contact with the stack some of the heat which it contains. When it is the turn of the second burner to operate, the combustion air heats up in contact with the stack, and the flame, following a path contrary to the preceding one, develops up to the first burner, the smoke in turn heating the stack associated with the first burner, and so on and so forth. This type of furnace is economical (a consumption typically of the order of 1,100 kcal/kg of glass), but has a more restricted capacity than transverse-burner furnaces. The burner pipes of these furnaces are constructed in a way similar to that used for the pipes of transverse-burner and regenerator furnaces, that is to say with a keyed vault.
Loop furnaces are generally used for the production of bottles.
The present invention is directed to making improvements to the construction of regenerator furnaces.